1. Technical Field
The present invention relates to an image scanning apparatus and, more particularly, a technique for an image scanning apparatus to detect a predetermined pattern that specifies a base position defining a scanning position.
2. Related Art
Image scanning apparatuses, or scanners, which optically scan an object using an image sensor and which generate image data based on the scanned result are widely used. Scanners generally use a position sensor to determine a scanning position. Another known method for determining a scanning position detects a pattern image from scanned image data using a predetermined pattern formed of, for example, black and white areas on the scanner, and determines a scanning position using the position of the detected pattern image as the reference (for example, JP-A-2000-113162).
In the case of the technique described in JP-A-2000-113162, the carriage is located in the vicinity of a home position at power-on, and the position of the predetermined pattern is specified by the relationship with the home position. However, scanners have the possibility that the carriage is located at a position different from the home position at power-on, for example, immediately after abnormal termination. In that case, the position of the predetermined pattern is not specified, which needs a process of detecting the predetermined pattern. The detection of the predetermined pattern is preferably executed quickly without fail.